Nowadays, a wheelchair is generally employed as a means of transportation for a patient or an aged person who cannot walk by themselves in hospital or for daily life. The electric wheelchair is a very common type of transportation for people who are patients, aged or for any reason cannot walk. The electric wheelchair comprises two front caster assemblies, two drive wheel assemblies, and two rear caster assemblies, pivotally assembled to a main frame, which supports the seat of the electric wheelchair. The front caster assemblies lead the movement and prevent toppling of the electric wheelchair. The drive wheel assemblies connect to a power control system of the wheelchair for driving the wheelchair. The rear caster assemblies keep balance of the electric wheelchair, especially for supporting the wheelchair in a stable mode when the wheelchair is climbing a slope. The stability of the electric wheelchair is the most important feature in driving the wheelchair. Coordinating the four caster assemblies is the key to maintaining the stability of an electric wheelchair, especially when the electric wheelchair is climbing a slope or on an uneven surface. Most front caster assemblies, drive wheel assemblies and rear caster assemblies of conventional electric wheelchairs are connected rigidly, so the caster assemblies cannot move independently relative to one another and the drive wheels to maintain balance automatically.
In conclusion, the conventional electric wheelchair, with rigidly mounted casters cannot satisfy people's requirements for stability when climbing a slope or traversing uneven terrain.